This invention relates in general to electrical connectors. More specifically, it relates to a field attachable connector for use down-hole in oil wells.
Electrical connectors for armored cables are particularly important in the production of oil. Submersible pumps are widely used in oil wells to extract the maximum volume of oil from the well site. Such pumps rest in the oil at the bottom of the well. Armored cables conduct electrical power from ground level to the pump. A typical cable has multiple conductors, each with their own insulation, surrounded by further insulation and an outer metallic jacket. The conductors are capable of carrying current at high power levels and at high voltages, for example, 2,400 volts. The armor jacket and heavy insulation are necessary to protect the conductors from both mechanical damage and the corrosive or explosive capabilities of fluids in the well such as liquid oil or water and flammable hydrocarbon gases that are often under very high pressures--several thousand pounds per square inch (psi).
In the past, during the installation of a submersible pump, the cable was introduced into the well in one continuous length strapped to the outside of a production tube used to conduct the oil to the surface. The straps were spaced at intervals to secure and control tension in the cable. The cable was simply pushed through the wellhead and then terminated in an electrical junction box. With this system, the principal use for splicing of the cable in the field was to repair mechanical damage to the cable.
Modern practice is to make electrical cable connection at the wellhead and between cable segments in down-hole packers (inflatable wellheads located down in the well casing). There is therefore a need to make an electrical connection (a splice) between the conductors of cable segments at a down-hole location. Because there has been a large growth in the use of submersible pumps, and because other components of the pump system have become more reliable (e.g. the cable, connectors, and pump motors), cable splices done in the field, typically by hand soldering, have become the weak link in the reliability of the entire pump system. Besides being unreliable, hand-splicing is also a comparatively time consuming and skilled procedure.
While connectors for armored cable are known, as for example the connector described in U.S. Pat. No. 3,945,700, they are not suited for splicing together the ends of two armored cables. Rather, they are designed primarily to connect the cable and its conductors to a socket of a conventional feed-through. As one example, the connector of the U.S. Pat. No. 3,945,700 , which is commonly assigned with the present application, is designed to secure the conductor to female contactor tubes that mate with contact pins in the feed-through socket. A threaded coupling ring rotatably mounted on the outside of the connector mechanically secures the connector to the feed-through socket. Because of this coupling arrangement, the connector must have a round cross-section. This is a significant disadvantage for a down-hole connector because it should fit in all standard size casings; this requires that the connector have a much lower profile than that offered by conventional round connectors.
Another difficulty with the U.S. Pat. No. 3,945,700 connector is that while it can be designed to accept cables with either a flat or round cross-sectional configuration, it does not provide a direct connection to another such cable, let alone one that may have a different configuration.
Because a down-hole connector operates in a hostile environment that may include a combustible gas under high pressure and fluids that can adversely affect the components of the cables, it must also protect the electrical components from the fluids and ensure that arcs or electrical resistance heating do not lead to an explosion or fire. While the U.S. Pat. No. 3,945,700 connector is sealed and in general designed to be explosion resistant, the rotating coupling ring may be susceptible to leaks where there are rapid fluctuations in pressure or temperature or when there is an aging of the sealing and mounting elements.
The U.S. Pat. No. 3,945,700 connector is also a comparatively complex structure with attendant disadvantages in its cost of manufacture. For example, the housing contains three molded rubber components, one metallic ring, and multiple contactor tube assemblies in electrical connection with the conductors. Mechanical connection of the connector to another element such as a socket requires a coupling sleeve and a coupling ring located principally at the exterior of the connector.
U.S. Pat. No. 4,073,559 to Lawson describes another connector for use down-hole in oil wells. It has tubular shells that are clamped together by a rotatable threaded sleeve 12. The connector is sealed by a lead washer that is pressed between the opposite end faces of the shells. Like the U.S. Pat. No. 3,945,700 connector discussed above, the Lawson U.S. Pat. No. 4,073,559 connector has a round cross-section that is not conducive to down-hole use and the sealing arrangement is not a reliable safeguard against the passage of explosive gases and corrosive fluids, especially under the aforementioned hostile operating conditions.
It is therefore a principal object of this invention to provide an electrical connector that can reliably splice together two armored electrical cables.
Another principal object of this invention is to provide such a splice connector which has a low profile and is designed to operate in an environment of high pressure fluids and gases, including combustible gases, so that it can be used for down-hole splicing in any standard size oil well casing.
Yet another object is to provide a connector with the foregoing advantages that can splice any combination of flat or round cables.
A further object is to provide a connector with the foregoing advantages that is field-attachable in a short period of time by comparatively unskilled workers using no special tools, tapes, fabrication, or soldering.
A still further object is to provide a connector with the foregoing advantages that has a long performance life despite operation in a hostile fluid environment.